Which Factor(s) Lead(s) to the Initiation of Most Urinary Tract

Which factor(s) lead(s) to the initiation of most urinary tract infections?

A) pathogen proximity to urethra to gain access to the urinary system
B) pathogens moving from kidney towards the bladder
C) common gut microflora such as E. coli and Proteus mirabilis moving from the digestive tract opening to the urinary tract
D) vaginal microflora such as Lactobacillus invading the urinary tract